UPDATE

Purpose

This statement is used to modify the values of existing fields in a table.

Syntax

UPDATE [hint_options] dml_table_clause
    SET update_asgn_list
    [ WHERE where_condition]
    [{ RETURNING | RETURN } returning_exprs [into_clause]]

dml_table_clause:
    dml_table_name opt_table_alias

update_asgn_list:
    column_name = expr [, expr...]

where_condition:
    expression

returning_exprs:
    projection_col_name [,projection_col_name ...]

into_clause:
    { INTO into_var_list | BULK COLLECT INTO into_var_list}

into_var_list:
    { USER_VARIABLE | ref_name } [,{ USER_VARIABLE | ref_name } ...]

Parameters

Example 1

Create a sample table tbl1 and insert test data.

obclient> CREATE TABLE tbl1(col1 INT PRIMARY KEY,col2 INT);
Query OK, 0 rows affected

obclient> INSERT INTO tbl1 VALUES(1,1),(2,2),(3,3),(4,4),(5,5);
Query OK, 5 rows affected
Records: 5  Duplicates: 0  Warnings: 0

obclient> SELECT * FROM tbl1;
+------+------+
| COL1 | COL2 |
+------+------+
|    1 |    1 |
|    2 |    2 |
|    3 |    3 |
|    4 |    4 |
|    5 |    5 |
+------+------+
5 rows in set

• Single-table update: Modify the col2 value of the row in tbl1 where tbl1.col1=1 to 100.

  obclient> UPDATE tbl1 SET tbl1.col2 = 100  WHERE tbl1.col1 = 1;
  Query OK, 1 row affected
  Rows matched: 1  Changed: 1  Warnings: 0
  
  obclient> SELECT * FROM tbl1;
  +------+------+
  | COL1 | COL2 |
  +------+------+
  |    1 |  100 |
  |    2 |    2 |
  |    3 |    3 |
  |    4 |    4 |
  |    5 |    5 |
  +------+------+
  5 rows in set
  

• Single-table update: Directly operate on the subquery to modify the col2 value of the row in the subquery where v.col1=1 to 10.

  obclient> UPDATE (SELECT * FROM tbl1) v SET v.col2 = 10 WHERE v.col1 = 1;
  Query OK, 1 row affected
  Rows matched: 1  Changed: 1  Warnings: 0
  
  obclient> SELECT * FROM tbl1;
  +------+------+
  | COL1 | COL2 |
  +------+------+
  |    1 |   10 |
  |    2 |    2 |
  |    3 |    3 |
  |    4 |    4 |
  |    5 |    5 |
  +------+------+
  5 rows in set
  

• Single-table update: Modify the col2 value of the rows in tbl1 where tbl1.col1<3 to 100.

  obclient> UPDATE tbl1 SET tbl1.col2 = 100 WHERE tbl1.col1 < 3;
  Query OK, 2 rows affected
  Rows matched: 2  Changed: 2  Warnings: 0
  
  obclient> SELECT * FROM tbl1;
  +------+------+
  | COL1 | COL2 |
  +------+------+
  |    1 |  100 |
  |    2 |  100 |
  |    3 |    3 |
  |    4 |    4 |
  |    5 |    5 |
  +------+------+
  5 rows in set
  

• Single-table update: The RETURNING clause returns the modified data.

  obclient> UPDATE tbl1 SET tbl1.col2 = 1000 WHERE tbl1.col1 = 1 RETURNING col2;
  +------+
  | COL2 |
  +------+
  | 1000 |
  +------+
  1 row in set
  
  obclient> SELECT * FROM tbl1;
  +------+------+
  | COL1 | COL2 |
  +------+------+
  |    1 | 1000 |
  |    2 |    2 |
  |    3 |    3 |
  |    4 |    4 |
  |    5 |    5 |
  +------+------+
  5 rows in set
  

Example 2

1. Create a sample table

   obclient> CREATE TABLE employees1 (
       id NUMBER,
       name VARCHAR2(20),
       salary NUMBER
   );
   

   obclient> CREATE TABLE employees2 (
       id NUMBER,
       name VARCHAR2(20),
       salary NUMBER
   );
   

2. Insert test data

   obclient> INSERT INTO employees1 VALUES (1, 'Jack', 5000);
   obclient> INSERT INTO employees2 VALUES (1, 'Tom', 3000);
   

3. Perform a table update operation using variables

    -- Declare variables
    DECLARE
        var_emp employees1%ROWTYPE;
    BEGIN
        -- Retrieve data from employees1 into the variable
        SELECT * INTO var_emp
        FROM employees1
        WHERE id = 1;
   
        -- Update the employees2 table using the variable
        UPDATE employees2
        SET (name) = (var_emp.name);
   
        COMMIT;
    END;
    /